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Hideaki Monjushiro

Publications and source records attributed to Hideaki Monjushiro.

12 recordsLinked to original sources
PubMed2006

Measurement of hydrolysis kinetics of galactose-substituted fluorescein by beta-galactosidase at the toluene-water interface by spinning microtube fluorometry.

A new analytical technique, spinning microtube fluorometry (SMF), was developed and applied to the study of interfacial hydrolysis of 5-dodecanoylaminofluorescein di-beta-D: -galactopyranoside (C12FDG) by beta-galactosidase (beta-gal) in the toluene-water system. The nonfluorescent lactone form of C12FDG in the toluene phase was converted at the interface to 5-dodecanoylaminofluorescein (C12F), which was fluorescent in the aqueous phase as a dianion at pH 7.3, though some part of C12F was extracted into the toluene phase as its nonfluorescent lactone form. The distribution ratios of C12FDG and C12F at pH 7.3 were determined as 1.4 x 10(2) and 1.97, respectively. The interfacial adsorption constants from the toluene phase to the interface at pH 7.3 were 4.8 x 10(-4) and 1.7 x 10(-2) dm for C12FDG and C12F, respectively. The kinetic experiments with the SMF method concluded that the rate-determining step of the enzymatic hydrolysis at the interface and in the aqueous phase was the 1:1 reaction of C12FDG and beta-gal and that the hydrolysis reaction rate constant at the interface at pH 7.3 was 1.84 x 10(3) M(-1)s(-1), almost equal to that in the aqueous solution, 1.76 x 10(3) M(-1)s(-1). Finally, the SMF method revealed that the contribution of the interfacial reaction to the overall hydrolysis reaction rate of the toluene-water system was as high as 97%.

Enzyme Stability↗
PubMed2006

Ion-association aggregation of an anionic porphyrin at the liquid/liquid interface studied by second harmonic generation spectroscopy.

Interfacial ion-association adsorption and aggregation of a water-soluble porphyrin, tetrakis(4-sulfonatephenyl)porphyrin (TPPS) diacid, which was promoted by a cationic cetyltrimethylammonium ion (CTA(+)), was studied by second harmonic generation (SHG) spectroscopy. Comparing the interfacial SH spectrum with the transmission absorption spectrum of TPPS in the aqueous solution elucidated the aggregation behavior of TPPS at the heptane/water interface. The time-dependent SHG spectra for TPPS aggregation and the interfacial tension lowering in the presence of CTA(+) were discussed on the basis of an electrostatic adsorption model. Then, it was suggested that TPPS diacid was highly concentrated by the ion-association with CTA(+) at the interface, which was the intermediate state before the final aggregated state.

Journal Article↗
PubMed2006

Magnetic susceptibility measurements of solutions by surface nanodisplacement detection.

A new principle to measure the magnetic susceptibility of a solution was proposed; it utilized the displacement of solution surface caused by the magnetic force applied to the solution. The interfacial displacement was measured with the sensitivity of 5 nm from a change of the interference fringes, so called Newton Ring, generated from the solution surface and an upper surface of a small plano-convex lens on the bottom wall of a cell. The surface displacement measurement was carried out in a homemade cell attached by one or two small Nd-Fe-B magnets. The performance of this method was investigated by the measurements of magnetic susceptibility of manganese(II) chloride solution and some lanthanide(III) solutions. An excellent linear relationship between the magnetic susceptibility and the interfacial displacement was observed for each solution system. Then, it was demonstrated that this relationship could be used for the determination of the magnetic susceptibility of solutions or the concentration of a solute by using the manganese(II) solution as a standard solution.

Journal Article↗
PubMed2005

Size sorting of biological micro-particles by Newton-ring nano-gap device.

The size determination and the size sorting of micrometer-sized particles were carried out by using a piezo-controlled nano-gap. The nano-gap was built by combining a plano-convex lens and a flat glass plate. The fabricated gap had a gradient, while the center of the lens was narrow and the outer side was wide. When the sample solution was injected into the gap, a meniscus force carried the sample particles toward the center of the lens with solvent evaporation; then the individual particle was trapped at the specific position where the particle diameter was equal to the gap distance. The size determination ability of this new method was certified by using the standard polystyrene particles and the size measurements of DNA molecules and yeast cells were demonstrated.

DNA↗
PubMed2004

Laser photophoretic migration with periodic expansion-contraction motion of photo-absorbing microemulsion droplets in water.

When the water-in-oil (w/o) microemulsion droplets including the Co(III)-pyridylazo complex as the photo-absorber were irradiated with a continuous-wave Ar(+) ion laser (514.5 nm), we have observed unexpected phenomenon that photo-absorbing microemulsion droplets in water repeated the expansion and the sudden contraction during the laser photophoretic migration. The period of the expansion-contraction cycle was inversely proportional to both the concentration of the complex and the irradiated laser power and was independent of the initial size of the droplet. The mechanism of the periodic motion of the droplet was investigated by local temperature measurement and Raman microscope spectroscopy. It was suggested that the first step was the phase separation of the bicontinuous microemulsion droplet into the normal w/o microemulsion outer phase and the aqueous inner phase in the droplet, which was caused by the laser-induced temperature gradient inside the droplet. Subsequently, an expansion of the inner aqueous phase was induced by the percolation of the external water by thermo-osmosis, which was caused by the laser-induced temperature gradient between the inside and the outside of the microemulsion liquid membrane of the droplet. When the liquid membrane became thinner to a critical thickness, the inner aqueous phase was released and the droplet shrank into the original size. The proposed mechanism can give an account of the unique cyclical motion.

Journal Article↗
PubMed2004

Micro-particle sorting by Newton-ring device.

A Newton-ring micro-particle sorter was constructed from a small convex lens and a flat glass. The sub-micrometer gap between them was controlled by a piezo-actuator and utilized for the fractionation of very small amounts of micro-particles in liquid.

Journal Article↗
PubMed2004

Cobalt(III) complexes of monodentate N9-bound adeninate (ade-), [Co(ade-kappaN9)Cl(en)2]+ (en = 1,2-diaminoethane): syntheses, crystal structures, and protonation behaviors of the geometrical isomers.

In acidic aqueous solution, a cobalt(III) complex containing monodentate N(9)-bound adeninate (ade(-)), cis-[Co(ade-kappaN(9))Cl(en)(2)]Cl (cis-[1]Cl), underwent protonation to the adeninate moiety without geometrical isomerization or decomposition of the Co(III) coordination sphere, and complexes of cis-[CoCl(Hade)(en)(2)]Cl(2) (cis-[2]Cl(2)) and cis-[Co(H(2)ade)Cl(en)(2)]Cl(3) (cis-[3]Cl(3)) could be isolated. The pK(a) values of the Hade and H(2)ade(+) complexes are 6.03(1) and 2.53(12), respectively, at 20 degrees C in 0.1 M aqueous NaCl. The single-crystal X-ray analyses of cis-[2]Cl(2).0.5H(2)O and cis-[3]Cl(2)(BF(4)).H(2)O revealed that protonation took place first at the adeninate N(7) and then at the N(1) atoms to form adenine tautomer (7H-Hade-kappaN(9)) and cationic adeninium (1H,7H-H(2)ade(+)-kappaN(9)) complexes, respectively. On the other hand, addition of NaOH to an aqueous solution of cis-[1]Cl afforded a mixture of geometrical isomers of the hydroxo-adeninato complex, cis- and trans-[Co(ade-kappaN(9))(OH)(en)(2)](+). The trans-isomer of chloro-adeninato complex trans-[Co(ade-kappaN(9))Cl(en)(2)]BF(4) (trans-[1]BF(4)) was synthesized by a reaction of cis-[2](BF(4))(2) and sodium methoxide in methanol. This isomer in acidic aqueous solution was also stable toward isomerization, affording the corresponding adenine tautomer and adeninium complexes (pK(a) = 5.21(1) and 2.48(9), respectively, at 20 degrees C in 0.1 M aqueous NaCl). The protonated product of trans-[Co(7H-Hade-kappaN(9))Cl(en)(2)](BF(4))(2).H(2)O (trans-[2](BF(4))(2).H(2)O) could also be characterized by X-ray analysis. Furthermore, the hydrogen-bonding interactions of the adeninate/adenine tautomer complexes cis-[1]BF(4), cis-[2](BF(4))(2), and trans-[2](BF(4))(2) with 1-cyclohexyluracil in acetonitrile-d(3) were investigated by (1)H NMR spectroscopy. The crystal structure of trans-[Co(ade)(H(2)O)(en)(2)]HPO(4).3H(2)O, which was obtained by a reaction of trans-[Co(ade)(OH)(en)(2)]BF(4) and NaH(2)PO(4), was also determined.

Adenine↗
PubMed2004

Interfacial aggregate growth process of Fe(II) and Fe(III) complexes with pyridylazophenol in solvent extraction system.

The complexation mechanism and aggregate formation of bis[2-(5-bromo-2-pyridylazo)-5-diethylaminophenolate] iron(II) and iron(III) complexes at the heptane-water interface were studied spectrophotometrically by the high-speed stirring method and the centrifugal liquid membrane method. Furthermore, the reduction process of the Fe(III) complex with ascorbic acid at the interface was spectrophotometrically observed. The chemical compositions of the interfacial aggregate of complexes have been proved by the X-ray photoelectron spectroscopy. The aggregation of the complex at the interface was observed as a red-shifted, very strong and narrower absorption band with respect to the absorption band of the monomer complex. The aggregate of Fe(III) complex showed more shifted spectrum than that of Fe(II) complex, which proposed the larger aggregation number of Fe(III) aggregate (n = 8) than that of Fe(II) aggregate (n = 3). The obtained rate constants of interfacial aggregation were smaller than rate constants of interfacial monomer complexation, because the formation of aggregate required the assembly of the monomers.

Journal Article↗
PubMed2004

Measurement of circular dichroism spectra of liquid/liquid interface by centrifugal liquid membrane method.

The direct measurement of the circular dichroism (CD) spectra of liquid/liquid interface has been achieved for the first time by the centrifugal liquid membrane (CLM) method combined with a conventional CD spectropolarimetry. In the sample chamber of the CD spectropolarimeter, a cylindrical glass cell containing small amounts of organic and aqueous phases was rotated at ca. 7000 rpm to generate a two-phase liquid membrane with a high specific interfacial area. The CD spectra of the J-aggregate of protonated 5,10,15,20-tetraphenylporphyrin formed at the toluene/sulfuric acid interface in the rotating cell have been measured. The results demonstrated the novelty and advantages of this method.

Journal Article↗
PubMed2004

Migration analysis of micro-particles in liquids using microscopically designed external fields.

The recent development of new migration methods of micro-particles in liquids using various external fields is reviewed. The combination of a laser scattering force and a photothermal effect produced photothermal-conversion laser-photophoresis. A dielectric field generated in a planer or a capillary quadrupole electrode realized dielectrophoresis. Using a micrometer-scaled magnetic field gradient, the "Magnetophoretic velocimetry" of micro-particles was invented. Furthermore, the Lorentz force generated by combining an electric field and a magnetic field was utilized for electromagnetophoresis. These new methods were overlooked and the advantages in analytical use were discussed.

Journal Article↗